Cholecystokinin impact on rainbow trout glucose homeostasis: Possible involvement of central glucosensors

• Published in: Regulatory peptides Vol. 172; no. 1-3; pp. 23 - 29
• Main Authors: Polakof, Sergio, Míguez, Jesus M., Soengas, José L.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 10.12.2011; Elsevier
• Subjects: Animals; Biological and medical sciences; Brain; Brain - drug effects; Brain - metabolism; Cholecystokinin; Cholecystokinin - pharmacology; Fundamental and applied biological sciences. Psychology; Glucose - metabolism; Glucose homeostasis; Glucosensing; Homeostasis - drug effects; Hypothalamus - drug effects; Hypothalamus - metabolism; Life Sciences; Liver; Liver - drug effects; Liver - metabolism; Oncorhynchus mykiss; Oncorhynchus mykiss - metabolism; Peptide Fragments - pharmacology; Rainbow trout; Vertebrates: endocrinology; Brain; Cholecystokinin; Glucosensing; Glucose homeostasis; Liver; Rainbow trout; Digestive system; Central nervous system; Homeostasis; Glucose; Neuropeptide; Encephalon
• ISSN: 0167-0115; 1873-1686
• DOI: 10.1016/j.regpep.2011.08.002

Although the role of cholecystokinin (CCK) on fish appetite regulation has been widely studied, its involvement in the regulation of glucose metabolism had been little explored to date. In the present study we have carried out different experimental approaches to study CCK effects in rainbow trout (a so-called ‘glucose intolerant’ fish species) glucose homeostasis. We have found that for the first time in a vertebrate species, systemic or central CCK administration causes hyperglycemia, which is at least in part related to the presence of an ancestral gut–brain axis in which CCK is involved. By using capsaicin we have found that part of the action of CCK on glucose homeostasis is mediated by vagal and splanchnic afferents. Changes in hepatic metabolism after systemic CCK administration suggest that the effects are not directly taking place on the liver, but probably in other tissues, while after the central CCK administration, the glycogenolytic response observed in liver could be mediated by the activation of the sympathetic system. In hypothalamus and hindbrain changes elicited by CCK-8 treatment are likely related to the glucosensor response to the increased glycemia and/or vagal/splanchnic afferences whereas in hindbrain a possible action through specific CCK-1 receptors cannot be excluded. All these processes result in changes in metabolic parameters related with glucose homeostasis control. Further studies are needed to fully understand the role of this peptide on glucose homeostasis control in fish. ► No information about CCK is available regarding glucose metabolism in fish. ► Both central and peripheral CCK administration caused hyperglycemia in trout. ► Changes in the brain glucosensing system are consistent with a gut–brain axis.